A shock absorber reduces the vibrations of the chassis spring. Together with the springs, they are the link between the wheel suspension and the body. When driving over potholes or obstacles, the suspension spring is first compressed. The shock absorber now dampens the spring's divergence and thus reduces the vibrations. That is why it is also called a vibration damper. There are two types of shock absorbers:
The gas pressure shock absorbers are the more modern of the two and are increasingly replacing the oil pressure shock absorbers. The oil contained in the oil shock absorbers contains approx. 10% of gas, which can be released from the liquid by the movement and become small bubbles. This process is called oil foaming. This reduces the damping force during the ride. This is the reason why the gas pressure shock absorbers were developed. Here, nitrogen is added to the vibration damper to keep the oil under pressure and thus prevent oil foaming. This means that the damping force remains constant even during long journeys. For this reason, gas pressure shock absorbers have been installed in most vehicles since 2000.
Vibrations are not only caused by unevenness of the road surface, but also by changes of direction or in curves. Shock absorbers and suspension springs are therefore logically subject to constant stress and should therefore be checked regularly.
A wear and tear of the shock absorbers is not always so easy to detect. Since vibration dampers wear out more and more over a longer period of time, a creeping change in the driving feel, such as a more unsteady steering behaviour, is not always noticed. Rumbling noises when driving slowly, on the other hand, draw attention to wear more quickly. An uneven or wavy tyre profile can be just as much an indication as leaking oil. This can be recognised by the varying depth or wavy profile. With the old oil-pressure shock absorbers you can also check whether oil is leaking. Then you should move the vehicle quickly to the workshop.
With the following test you can check the functioning of the shock absorbers of your vehicle yourself:
However, the test only provides an indication of the condition of the shock absorbers. Reliable results can only be obtained in the workshop.
A defective vibration damper affects the chassis and thus the driving safety. When cornering, the tyres lose lateral support, the vehicle reacts spongy and tilts outwards. On the motorway, the vehicle can become susceptible to side winds with one or more defective shock absorbers. In curves, defective shock absorbers can cause the vehicle to skid.
In addition, the vehicle may "kangaroo jump" while driving. The vehicle then "hops" over the road because the vibration dampers no longer stabilize it (so well). If the damage is not yet so large, then it is often only noticeable at night when the headlights "dance" on the road.
Aquaplaning also occurs faster. If frequent steering corrections are necessary when driving, this could also be an indication of defective shock absorbers. As the grip of the tyres is reduced, the vehicle not only has less stability but also a longer braking distance. Furthermore, the function of the ABS is limited if the axles have different degrees of suspension. The vibration dampers therefore not only ensure driving comfort, but also safe road holding and therefore first and foremost your safety!
If the above mentioned symptoms occur, we recommend to have the shock absorbers and suspension springs checked directly in the workshop. Vibration dampers should always be replaced axle by axle, to keep the damping deviations as small as possible. The general recommendation is to have the dampers checked after about 80,000 kilometers at the latest. We recommend to have the exchange only done by an expert or with experience. If you are not sure which shock absorbers are suitable for your vehicle, please contact our customer service with the 17-digit chassis number.